JP7487432B1 - Convection Oven - Google Patents

Abstract

[Problem] To provide a convection oven capable of effectively performing radiant heating and convection heating while taking into consideration the characteristics of the heater. [Solution] The convection oven 1 of the present invention comprises a heating chamber 120 for heating an object to be heated, a cooking tray receiver 130 provided on both side walls of the heating chamber 120, a blower 140 disposed in a blower chamber 121 formed through the top wall of the heating chamber 120, and a plurality of heating members 150 equipped with heating elements that generate heat when electricity is passed through them, the heating members 150 including, as upper heater 150A, sheathed heaters 151A, 151B formed by surrounding a nichrome wire with a metal pipe and emitting mainly far infrared rays, and a carbon heater 152A formed by surrounding a carbon filament with a glass tube and emitting mainly mid infrared rays, the sheathed heater 151A used as the upper heater is disposed so as to receive air supplied from a blower port 122, and includes a sheathed heater 151B as a lower heater 150B. [Selected Figure] Figure 1

Description

The present invention relates to convection ovens, and in particular to technology for effectively cooking food in a variety of cooking modes.

A convection oven is equipped with a tray on which the food to be heated, such as bread or pizza, is placed within a heating chamber, and heaters that generate heat through resistance heating are disposed above and below the tray within the heating chamber, and the food to be heated on the tray is cooked by radiant heat from the heaters. In addition, the air blown into the heating chamber by a blower is heated by the heat from the heater and convected, thereby achieving uniform heating through convection.

Conventional convection ovens often use sheathed heaters, whose surface becomes very hot. Sheathed heaters are formed by surrounding a nichrome wire, which generates heat when electricity is passed through it, with a metal pipe placed between them and an insulator. The metal pipe surrounding the nichrome wire has a high thermal conductivity, making it easy to transfer heat to the airflow, and sheathed heaters are often used as heating elements for convection ovens.

Now, a sheathed heater is a heater that mainly radiates so-called far-infrared rays, which have a long wavelength among infrared rays. Compared to near-infrared and mid-infrared rays, which have a short wavelength, far-infrared rays can heat the surface of an object more effectively, but they cannot reach the inside of an object, making it difficult to heat the inside of an object. In addition, the heater itself has a weakness in that it is slow to heat up, and the start-up speed is slow. Therefore, when using a sheathed heater for oven cooking, it takes a long time to preheat. Furthermore, they have poor response to the power being applied, so heating elements using sheathed heaters generally have poor controllability.

As a result, when using a convection oven with only a sheath heater to cook food that requires slow heating, such as roasted chicken, gratin, or baked goods, not only does it take a long time to preheat and cook, but the surface may burn and the inside may not be cooked through.

In addition, while convection ovens are required to slowly heat food such as roasted chicken, gratin, and baked goods, they are also required to heat to high temperatures in a relatively short time, such as toasting bread or baking pizza. However, with convection ovens that use only a sheath heater, it is difficult to heat food to a crisp in a short time.

In light of this situation, technology has been proposed to create a convection oven using various types of heaters (Patent Document 1).

The convection oven described in Patent Document 1 is equipped with a first heater that emits far-infrared rays near the ceiling wall that divides the heating chamber, and a second heater that contributes to convection heating on the rear wall. The combination of the first heater that emits far-infrared rays and the second heater that contributes to convection heating provides effective heating.

However, even in a convection oven such as that disclosed in Patent Document 1, radiant heating relies on a first heater that emits far-infrared rays, which have poor responsiveness, making it difficult to cook food such as toasting bread to a crisp in a short time.

In addition, if a heater that radiates near-infrared or mid-infrared rays, which have a short warm-up time and easily penetrate into an object, is used as a heater for convection heating, the filament that generates heat when electricity is passed through it is surrounded by a glass tube such as quartz glass, so the surface temperature of the glass tube is low and the thermal conductivity of the glass tube is not high, so the heat generated by the filament cannot be effectively converted into convection heat.

JP 2022-088138 A

The present invention was made in consideration of these problems, and aims to provide a convection oven that can effectively perform radiant heating and convection heating while taking into account the characteristics of the heater.

The present invention provides the following solutions:

The convection oven according to the first feature comprises a heating chamber for heating the object to be heated, a cooking dish tray provided on both side walls of the heating chamber and for placing a cooking dish on which the object to be heated is placed, a blower arranged in a blower chamber formed through the top wall of the heating chamber and supplying air to the heating chamber from a blower port provided in the top wall, and a plurality of heating elements having heating elements that generate heat when electricity is passed through them, the heating elements including a sheathed heater formed by surrounding a nichrome wire with a metal pipe and emitting mainly far-infrared rays, and a carbon heater formed by surrounding a carbon filament with a glass tube and emitting mainly mid-infrared rays, the sheathed heaters being arranged to receive air supplied from the blower port.

According to the invention relating to the first feature, not only is a sheathed heater that emits far-infrared rays used as a heating element, but also a carbon heater that emits mid-infrared rays that have a short warm-up time and easily penetrate into the interior of an object, so that heat can be applied thoroughly to the interior while shortening preheating and heating times. In addition, the sheathed heater is surrounded by a metal pipe with a high thermal conductivity and is positioned to receive air supplied from the air outlet, so that the heat emitted from the sheathed heater can be effectively transferred to the air flow, generating large convection heat and improving the heating performance as a convection oven.

The invention according to the second characteristic is the invention according to the first characteristic, in which the air outlets are multiple openings arranged closely together on the central side of the top wall, the heating member includes an upper heater arranged above the cooking dish holder, and the upper heater includes multiple sheath heaters and carbon heaters, with the carbon heaters arranged closer to the end of the top wall than the sheath heaters.

According to the invention relating to the second feature, since the air outlets are multiple openings densely arranged on the center side of the top wall, an air flow can be generated in a substantially vertical downward direction toward the heating chamber, and the high-temperature air that tends to stagnate in the upper part of the heating chamber can be uniformly circulated in the heating chamber. In addition, although the carbon heater is surrounded by a glass tube that is weak against impact, it is used as an upper heater arranged above the cooking dish holder, so the risk of damage due to contact with objects can be reduced. Moreover, since the carbon heater is arranged on the end side of the top wall more than the sheathed heater, the risk of contact with objects is further reduced. Furthermore, since multiple sheathed heaters are arranged to receive air supplied from the air outlets arranged on the center side of the top wall, and multiple carbon heaters are arranged on the end side of the sheathed heater, when heating by convection, the heat emitted from the sheathed heater is mainly used. And, when heating by radiation, radiant heat can be emitted from the carbon heaters arranged on both ends of the top wall toward the entire cooking dish, and uniform radiation heating can be performed.

The third feature of the invention is the second feature of the invention, and includes a sheath heater located approximately directly below the air outlet.

According to the third feature of the invention, the sheathed heater is placed almost directly below the air outlet, so the heat generated by the sheathed heater can be directly transferred to the air blown almost vertically downward from the air outlet, and a large amount of convection heat can be generated even with a small amount of electricity.

The invention according to the fourth feature is an invention according to any one of the first to third features, which includes a lower heater disposed below the cooking dish support, and the lower heater includes a sheath heater formed by surrounding a nichrome wire with a metal pipe and emitting mainly far infrared rays.

According to the fourth feature of the invention, a lower heater is provided below the cooking dish holder, so heat can be effectively applied by utilizing heat generated at the bottom of the heating chamber. In addition, a sheathed heater surrounded by a metal pipe is used as the lower heater, so damage to the heater due to objects falling on it, etc. can be prevented.

The present invention provides a convection oven that can effectively perform radiant heating and convection heating while taking into account the characteristics of the heater.

Fig. 1 is a front perspective view of a convection oven according to the present invention, Fig. 1(a) shows a state seen from diagonally below, and Fig. 1(b) shows a state seen from diagonally above. 2A and 2B are perspective views of the convection oven according to the present invention as viewed from the front, with Fig. 2A showing a state as viewed from diagonally above and Fig. 2B showing a state as viewed from diagonally below. FIG. 3 is a cross-sectional view taken along line AA in FIG.

Below, a description will be given of an embodiment of the present invention with reference to the drawings. Note that this is merely an example, and the technical scope of the present invention is not limited to this example.

The overall configuration of the convection oven 1 according to this embodiment will be described using Figures 1 to 3.

Figure 1 is a perspective view of a convection oven according to the present invention as seen from the front. Figure 1(a) shows the state as seen from diagonally below, and Figure 1(b) shows the state as seen from diagonally above. Figure 2 is a perspective view of a convection oven according to the present invention as seen from the front. Figure 2(a) shows the state as seen from diagonally above, and Figure 2(b) shows the state as seen from diagonally below. Figure 3 is a cross-sectional view taken along line A-A in Figure 2(b).

As shown in Figures 1 and 2, the convection oven 1 according to the present invention is composed of a convection oven body 110, a heating chamber 120, a cooking dish holder 130, a blower 140, a heater 150, an operation unit 160, and a control unit (not shown).

The convection oven body 110 is formed in a roughly rectangular parallelepiped shape and defines a heating chamber 120 inside. A front opening is provided on the front of the convection oven body 110, through which the object to be heated can be put in and taken out, and the front opening is covered by a door 111 that can be opened and closed.

The heating chamber 120 heats an object to be heated placed on a cooking tray (not shown) using a heater 150 and a blower 140, and has a roughly rectangular shape. The heating chamber 120 has a roughly rectangular top wall 121 that defines its upper end, and the top wall 121 is provided with a blower 122 for supplying airflow from the blower 140 (described later) into the heating chamber 120. The blower 122 is a number of openings arranged concentrically so that the central side of the roughly rectangular top wall 121 is densely packed.

The cooking dish support 130 is for placing a cooking dish (not shown) on which an object to be heated is placed, and in this embodiment, is configured by a step portion formed in the front-rear direction at a predetermined height on the left and right wall portions. That is, when the door body 111 is open, the cooking dish (not shown) is slid in the front-rear direction along the cooking dish support 130 to be attached to and detached from the heating chamber 120. Note that in this embodiment, the cooking dish support 130 is provided at multiple heights, and the height at which the cooking dish is placed can be changed depending on the size of the object to be heated and the cooking mode set by the operation unit 160.

The blower 140 generates an airflow for convection heating of the object to be heated in the heating chamber 120, and is installed in a blower chamber 141 formed above the top wall 121 that constitutes the heating chamber 120, as shown in FIG. 3. The rotating shaft of the blower 140 extends in a substantially vertical direction, and an airflow is generated by driving the rotating shaft by a motor (not shown). The top wall 121 is provided with an air outlet 122, and the airflow generated by the blower 141 flows substantially vertically downward from the air outlet 122 toward the heating chamber 120.

The heating member 150 is a heating element for generating radiant heat and convection heat, and is equipped with a heating element that generates heat when electricity is applied. In this embodiment, the convection oven 1 is equipped with multiple types of heating members 150, and is equipped with an upper heater 150A in the upper part of the heating chamber 120, i.e., above the cooking dish receiver 130, and a lower heater 150B in the lower part of the heating chamber 120, i.e., below the cooking dish receiver 130, as the heating member 150.

As shown in FIG. 1(a) and FIG. 2(a), the upper heater 150A includes a sheath heater 151A formed by surrounding a nichrome wire with a metal pipe and emitting mainly far infrared rays, and a carbon heater 152A formed by surrounding a carbon filament with a glass tube and emitting mainly mid-infrared rays. The sheath heater 151A constituting the upper heater 150A is disposed along the width direction directly below the air outlet 122 so as to receive air supplied from the air outlet 122. In addition, no reflector or the like is provided around the sheath heater 151A, so that the heater surface receives air and can directly transfer heat. The carbon heater 152A constituting the upper heater 150A is disposed along the width direction at a position farther from the air outlet 122 than the sheath heater 151A. As shown in FIG. 3, in this embodiment, the upper heater 150A is composed of two sheathed heaters 151A and two carbon heaters 152A, with the two sheathed heaters 151A located directly below the air outlet 122 and toward the center of the heating chamber 120 in the front-to-rear direction, and the two carbon heaters 152A located closer to the end of the heating chamber 120 in the front-to-rear direction than the sheathed heaters 151A.

In general, sheathed heaters are formed by surrounding a nichrome wire, which acts as a heating element, with a metal pipe, and mainly emit far-infrared rays. Far-infrared rays do not penetrate easily into objects, so only the very surface (0.1 to 0.2 mm) is heated. The maximum temperature of the heater is 600 to 800°C, and the radiated heat density is about 5 W/cm2, so the energy density is low. In addition, it takes several minutes to start up, and the responsiveness to current flow is low. Due to these characteristics, sheathed heaters are suitable for searing the surface, but heat is not easily transmitted to the inside of the heated object, making them unsuitable for slowly heating large objects.

Carbon heaters, on the other hand, are formed by surrounding a carbon filament, which is the heating element, with an insulator such as an inert gas in a quartz glass tube, and mainly emit mid-infrared radiation. Mid-infrared radiation easily penetrates into the interior of an object, making it suitable for heating the interior of a lump of heated material, especially one that contains a lot of moisture. The maximum temperature of the heater is 900-1,100°C, and the radiated heat density is about 14 W/cm2, making it a high energy density. It has a short start-up time of just a few seconds, excellent responsiveness to current flow, and easy temperature control.

In this embodiment, a sheath heater 151A and a carbon heater 152A are used in combination as the upper heater 150A.

As shown in Fig. 1(b) and Fig. 2(b), the lower heater 150B includes a sheathed heater 151B that is formed by surrounding a nichrome wire with a metal pipe and mainly emits far infrared rays. As shown in Fig. 3, the sheathed heater 151B that constitutes the lower heater 150B is arranged in two pieces along the width direction near the bottom wall of the heating chamber 120.

The operation unit 160 is formed on the upper front surface of the convection oven body 110 and is composed of knobs for operating and setting the heating time and cooking mode.

The convection oven 1 configured in this way uses not only the sheath heaters 151A and 152A that emit far-infrared rays as the heating elements 150, but also the carbon heater 151B that emits mid-infrared rays that have a short warm-up time and easily penetrate into the interior of an object, so it is possible to shorten the preheating and heating times while still thoroughly applying heat to the interior. In addition, the use of a sheath heater and a carbon heater in combination allows infrared rays of a wide range of wavelengths to be emitted simultaneously, recreating the infrared wavelengths of charcoal grilling, which is ideal for searing and other cooking, thereby improving the taste of the heated food.

In addition, the sheathed heater 151A, which is surrounded by a metal pipe with a high thermal conductivity, is arranged to receive air supplied from the air outlet 122, so that the heat generated by the sheathed heater 151A can be effectively transferred to the air flow, generating a large amount of convection heat and improving the heating performance of the convection oven 1.

Since the air outlets 122 are multiple openings densely arranged on the central side of the top wall, an air flow can be generated in a substantially vertical downward direction toward the heating chamber 120, and the high-temperature air that tends to stagnate in the upper part of the heating chamber 120 can be circulated uniformly within the heating chamber 120. In addition, although the carbon heater 152A is surrounded by a glass tube that is vulnerable to impacts, it is used as the upper heater 150A disposed above the cooking dish support 130, reducing the risk of damage due to contact with objects, etc.

In addition, the carbon heater 152A is disposed closer to the end of the top wall than the sheathed heater 151A, so there is less risk of contact with objects. Furthermore, since multiple sheathed heaters 151A are disposed to receive air supplied from the air outlet 122 disposed at the center of the top wall, and multiple carbon heaters 152A are disposed closer to the end than the sheathed heater 151A, when heating by convection, the heat emitted from the sheathed heater 151A is mainly used. When heating by radiation, radiant heat can be emitted from the carbon heaters 152A disposed at both ends of the top wall toward the entire cooking dish, allowing for uniform radiation heating.

In addition, because the sheathed heater 151A is installed approximately directly below the air outlet 122, the heat generated by the sheathed heater 151A can be directly transferred to the air blown approximately vertically downward from the air outlet 122, and a large amount of convection heat can be generated even with a small amount of electricity.

In addition, since it is equipped with a lower heater 150B arranged below the cooking dish receiver 130, heat generated at the bottom of the heating chamber 120 can be used to effectively apply heat. Also, since a sheathed heater 151B surrounded by a metal pipe is used as the lower heater 150B, the heater is less likely to be damaged even if an object falls, and it can be used safely. In particular, by using the sheathed heater 151A arranged as the upper heater 150A and the sheathed heater 151B arranged as the lower heater 150B in combination, it becomes easier to control the multi-function oven during low-temperature cooking.

When using a convection oven 1 configured as described above to toast bread, for example, although it is necessary to apply heat to the inside of the bread, the main heating required is to brown the surface. In this case, heating using the sheathed heaters 151A and 151B is suitable, but since the sheathed heaters 151A and 151B take time to heat up, cooking takes a long time if they are used alone. For this reason, a heating method is required that uses both the carbon heater 151B and the sheathed heaters 151A and 151B to complete heating in a short time while still allowing the surface to be nicely browned.

In this embodiment, the carbon heater 152A is configured as the upper heater 150A and is disposed at the same height as the sheath heater 151A, but this is not limited thereto, and the heater may be disposed at another height as long as it can provide effective heating by radiation.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Furthermore, the effects described in the embodiments of the present invention are merely a list of the most favorable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments of the present invention.

The above-mentioned embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to having all of the configurations described.

The convection oven of this invention is useful as a cooking device for heating and cooking foods such as bread.

Reference Signs List 1 Convection oven 110 Convection oven body 120 Heating chamber 130 Cooking tray holder 140 Blower 150 Heating member 150A Upper heater 151A Sheathed heater 151B Carbon heater 150B Lower heater 151B Sheathed heater 160 Operation unit

Claims (2)

A heating chamber for heating an object to be heated;
A cooking tray holder is provided on both side walls of the heating chamber and is used to place a cooking tray on which the object to be heated is placed;
a blower that is disposed in a blower chamber formed through a top wall of the heating chamber and supplies air to the heating chamber through an air outlet provided in the top wall;
A plurality of heating members each having a heating element that generates heat when energized;
The heating member includes an upper heater disposed above the cooking dish support, the upper heater being a sheath heater formed by surrounding a nichrome wire with a metal pipe and emitting mainly far infrared rays, and a carbon heater formed by surrounding a carbon filament with a glass tube and emitting mainly mid-infrared rays,
a sheathed heater used as the upper heater is disposed so as to receive air supplied from the air outlet ;
The heating member includes a lower heater disposed below the cooking dish tray, the lower heater being formed by surrounding a nichrome wire with a metal pipe and emitting mainly far infrared rays.
Convection oven. The sheath heater is provided substantially directly below the air outlet.
2. The convection oven of claim 1.